Seventy phytoplasma isolates, including 10 previously characterized reference strains, of the aster yellows group were examined by RFLP analysis of PCR-amplified rDNA and RFLP and sequence analysis of the tuf gene. On the basis of rDNA restriction profiles, seven previously proposed 16S rDNA subgroups (16SrI-A, -B, -C, -D, -E, -F and -K) were recognized in the material examined. In addition, th...

Nucleotide excision repair (NER) removes a plethora of DNA lesions. It is performed by a large multisubunit protein complex that finds and repairs damaged DNA in different chromatin contexts and nuclear domains. The nucleolus is the most transcriptionally active domain, and in yeast, transcription-coupled NER occurs in RNA polymerase I-transcribed genes (rDNA). Here we have analyzed the roles o...

To determine whether heterogeneity exists in the organization or redundancy of the rRNA cistrons of inbred populations of Drosophila melanogaster, we have derived a number of sublines from the strains Oregon R and Canton S. These two strains were chosen because our previous studies have demonstrated a difference in the competence of these strains to exhibit a "compensatory response" of the rDNA...

The nuclear genome harbours hundreds to several thousand copies of ribosomal DNA. Despite their essential role in cellular ribogenesis few studies have addressed intrapopulation, interpopulation and interspecific levels of rDNA variability in wild plants. Some studies have assessed the extent of rDNA variation at the sequence and copy-number level with large sampling in several species. However...

Sequence analysis of the small subunit ribosomal DNA (SSU-rDNA) and elongation factor 1 alpha (ef1α) was performed on Giardia cysts isolated from faeces collected from a quenda (Isoodon obesulus) in the southwest of Western Australia. The SSU-rDNA and ef1α were sequenced in their entirety and correspondingly aligned with the published sequence information of other known species and genotypes of...

Eco1 is the acetyltransferase that establishes sister-chromatid cohesion during DNA replication. A budding yeast strain with an eco1 mutation that genocopies Roberts syndrome has reduced ribosomal DNA (rDNA) transcription and a transcriptional signature of starvation. We show that deleting FOB1--a gene that encodes a replication fork-blocking protein specific for the rDNA region--rescues rRNA p...

R2 non-LTR retrotransposons exclusively insert into the 28S rRNA genes of their host, and are expressed by co-transcription with the rDNA unit. The grasshopper Eyprepocnemis plorans contains transcribed rDNA clusters on most of its A chromosomes, as well as non-transcribed rDNA clusters on the parasitic B chromosomes found in many populations. Here the structure of the E. plorans R2 element, it...

DNA corresponding to 16S rDNA and the 165-23S rDNA intergenic spacer (ITS) from 22 reference strains of acetic acid bacteria, representing the diversity of the family Acetobacteraceae, and 24 indigenous acetic acid bacteria isolated from wine fermentations were analysed by PCR-RFLP. Frateuria aurantia LMG 1558T and Escherichia coli ATCC 11775T were included as outgroups. PCR-amplified products ...

The Rif1 protein is a negative regulator of DNA replication initiation in eukaryotes. Here we show that budding yeast Rif1 inhibits DNA replication initiation at the rDNA locus. Absence of Rif1, or disruption of its interaction with PP1/Glc7 phosphatase, leads to more intensive rDNA replication. The effect of Rif1-Glc7 on rDNA replication is similar to that of the Sir2 deacetylase, and the two ...